JP7468631B2 - Method for producing alkenyl group-containing organopolysiloxane - Google Patents

Description

The present invention relates to a method for producing an alkenyl group-containing organopolysiloxane. More specifically, the present invention relates to a method for producing an alkenyl group-containing organopolysiloxane in an industrially advantageous manner by a simple process of polymerizing a mixture of raw materials in the presence of a cation exchange resin.

It has been widely known that the production of alkenyl group-containing organopolysiloxanes is carried out using linear or cyclic organopolysiloxanes as raw materials and strong acids or strong bases as catalysts. For example, Non-Patent Document 1 shows a production example using hydrochloric acid, sulfuric acid, phosphoric acid, trifluoromethanesulfonic acid, etc. as strong acids and sodium hydroxide, potassium hydroxide, or silanolates of these, etc. as strong bases.

On the other hand, many applications of alkenyl group-containing organopolysiloxanes have been reported, including curable organopolysiloxane compositions in which platinum group metal catalysts are added to the organopolysiloxane and organohydrogenpolysiloxane. It has long been known that the composition is used as a release sheet formed on the surface of a substrate to prevent adhesion or fixation between sheet-like substrates such as paper and plastic and adhesive materials (Patent Document 1: JP 47-32072 A). This method of forming a cured film by hydrosilylation reaction is widely used because it has excellent curability and can meet various release property requirements, from light to heavy release.

Curable organopolysiloxane compositions that cure to form a film through a hydrosilylation reaction include those in which the composition is dissolved in an organic solvent, those in which the composition is dispersed in water using an emulsifier to form an emulsion, and those that do not contain a solvent. Solvent-based types have the disadvantage of being harmful to the human body and the environment. Emulsion-based types require high energy to remove the water, and furthermore, because the emulsifier remains, there is a problem that the resulting cured film has reduced adhesion to the substrate. For this reason, solvent-based curable organopolysiloxane compositions have been widely used in recent years.

From the viewpoint of coatability, solventless curable organopolysiloxane compositions use alkenyl group-containing organopolysiloxanes with relatively low viscosity, and due to the increasing demand as mentioned above, there is a need for the production of alkenyl group-containing organopolysiloxanes with more stable quality and greater productivity at lower cost.

The use of solid catalysts such as ion exchange resins has been reported as a highly productive production method. For example, Patent Document 2 (JP Patent Publication No. 2012-512272) describes a method for producing siloxanes comprising a step of reacting at least two siloxanes in the presence of an ion exchange resin catalyst containing 6 to 19% by mass of water relative to the dry mass of the ion exchange resin catalyst. By specifying the water content in the ion exchange resin catalyst, it is possible to shorten the reaction time and reuse the ion exchange resin catalyst, but the water content must be adjusted during the reaction, making the process complicated. Furthermore, what is produced is an organohydrogenpolysiloxane, and no mention is made of alkenyl-group-containing organopolysiloxanes.

Patent Document 3 (JP 2011-219647 A) describes a method for producing silanol group-containing organosilanes and organopolysiloxanes in which organoalkoxysilane and water are continuously passed through a cylindrical container filled with a cation exchange resin. Although this is a highly productive production method in which the materials are continuously passed through a cylindrical container, it is only about a method for producing silanol group-containing organopolysiloxanes and does not mention alkenyl group-containing organopolysiloxanes.

Patent Documents 4 to 6 (JP 2012-140391 A, JP 2013-36000 A, JP 7-316299 A) describe methods for producing organopolysiloxanes using various ion exchange resins, but the functional groups contained are silanol groups, amino groups, and (meth)acrylic groups, and no mention is made of alkenyl group-containing organopolysiloxanes. In addition, the reaction time is extremely long, from 5 to 24 hours, so none of these production methods can be said to be highly productive.

Japanese Patent Application Laid-Open No. 47-32072 JP 2012-512272 A JP 2011-219647 A JP 2012-140391 A JP 2013-36000 A Japanese Patent Application Laid-Open No. 7-316299

Silicone Handbook (edited by Kunio Ito, published by Nikkan Kogyo Shimbun)

The present invention has been made in consideration of the above circumstances, and aims to provide an alkenyl group-containing organopolysiloxane having a relatively low viscosity, and to provide a method for producing the organopolysiloxane with higher productivity and lower cost.

As a result of intensive research into achieving the above-mentioned object , the present inventors have found that the above-mentioned object can be achieved by a production method in which a cyclic organopolysiloxane and a linear or branched organopolysiloxane having an alkenyl group are mixed in a specific ratio and polymerized in the presence of a cation exchange resin that is substantially free of water for a reaction time of 60 minutes or less, thereby completing the present invention.

（式中、Ｒ¹は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、ａは３≦ａ≦６を満たす整数である。）
で表される環状オルガノポリシロキサンと、
（ａ２）下記平均組成式（２）：

（式中、Ｒ²は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、ｂは２以上の整数であり、ｃは０以上の整数であり、ｄは０以上の整数であり、ｅは０以上の整数であり、及び２≦ｂ＋ｃ＋ｄ＋ｅ≦５０である。ただし、前記Ｒ¹及びＲ²のうち少なくとも２個はアルケニル基である。）
で表される直鎖又は分岐状オルガノポリシロキサンとを
（ａ１）成分中のＲ¹ ₂ＳｉＯ_2/2単位と（ａ２）成分とをモル比で１：１～４９８：１の割合で配合し、
（ａ３）水を実質的に含有しない陽イオン交換樹脂
の存在下、反応時間６０分以内で重合させることを特徴とする、下記平均組成式（３）で表されるアルケニル基含有オルガノポリシロキサンの製造方法。

（式中、Ｒ³は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、Ｒ³のうち少なくとも２個はアルケニル基であり、ｆは２以上の整数であり、ｇは３以上の整数であり、ｈは０以上の整数であり、ｉは０以上の整数であり、及び１０≦ｆ＋ｇ＋ｈ＋ｉ≦５００である。）
［２］
前記（ａ１）成分及び（ａ２）成分の混合液を、前記陽イオン交換樹脂を充填したカラムに連続的に通過させ重合を行う［１］記載のアルケニル基含有オルガノポリシロキサンの製造方法。
［３］
前記陽イオン交換樹脂が、水分含有率１．６質量％以下である［１］又は［２］記載のアルケニル基含有オルガノポリシロキサンの製造方法。
［４］
前記陽イオン交換樹脂が、スチレンジビニルベンゼンスルホン酸共重合体である［１］～［３］のいずれかに記載のアルケニル基含有オルガノポリシロキサンの製造方法。
［５］
前記平均組成式（３）で表されるアルケニル基含有オルガノポリシロキサンの２５℃における粘度が、１～１，０００ｍＰａ・ｓである［１］～［４］のいずれかに記載のアルケニル基含有オルガノポリシロキサンの製造方法。 That is, the present invention provides the following method for producing an alkenyl-containing organopolysiloxane.
[1]
(a1) The following general formula (1):

(In the formula, ^R1 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is an integer satisfying 3≦a≦6.)
A cyclic organopolysiloxane represented by the formula:
(a2) The following average composition formula (2):

(In the formula, R ² 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, b is an integer of 2 or more, c is an integer of 0 or more, d is an integer of 0 or more, e is an integer of 0 or more, and 2≦b+c+d+e≦50, with the proviso that at least two of R ¹ and R ² are alkenyl groups.)
and _a ^linear or branched organopolysiloxane represented by _the following formula:
(a3) A method for producing an alkenyl-containing organopolysiloxane represented by the following average composition formula (3), which comprises polymerizing the alkenyl group in the presence of a cation exchange resin that is substantially free of water for a reaction time of 60 minutes or less:

(In the formula, R3 ^'s are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, at least two of the ^R3 's are alkenyl groups, f is an integer of 2 or greater, g is an integer of 3 or greater, h is an integer of 0 or greater, i is an integer of 0 or greater, and 10≦f+g+h+i≦500.)
[2]
The method for producing an alkenyl group-containing organopolysiloxane according to [1], wherein the polymerization is carried out by continuously passing a mixed liquid of the components (a1) and (a2) through a column packed with the cation exchange resin.
[3]
The method for producing an alkenyl group-containing organopolysiloxane according to [1] or [2], wherein the cation exchange resin has a water content of 1.6 mass% or less.
[4]
The method for producing an alkenyl group-containing organopolysiloxane according to any one of [1] to [3], wherein the cation exchange resin is a styrene-divinylbenzenesulfonic acid copolymer.
[5]
The method for producing an alkenyl group-containing organopolysiloxane according to any one of [1] to [4], wherein the viscosity of the alkenyl group-containing organopolysiloxane represented by the average composition formula (3) at 25° C. is 1 to 1,000 mPa·s.

According to the manufacturing method of the present invention, it is possible to produce alkenyl group-containing organopolysiloxanes with higher productivity, lower cost, and through simplified steps compared to conventional manufacturing methods that use strong acids or strong bases as catalysts.

（式中、Ｒ³は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、Ｒ³のうち少なくとも２個はアルケニル基であり、ｆは２以上の整数であり、ｇは３以上の整数であり、ｈは０以上の整数であり、ｉは０以上の整数であり、及び１０≦ｆ＋ｇ＋ｈ＋ｉ≦５００である。） The production method of the present invention will now be described in more detail.
The present invention provides a method for producing an alkenyl-containing organopolysiloxane. The alkenyl-containing organopolysiloxane obtained by this method is represented by the following average composition formula (3).

(In the formula, R3 ^'s are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, at least two of the ^R3 's are alkenyl groups, f is an integer of 2 or greater, g is an integer of 3 or greater, h is an integer of 0 or greater, i is an integer of 0 or greater, and 10≦f+g+h+i≦500.)

（式中、Ｒ¹は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、ａは３≦ａ≦６を満たす整数である。）

（式中、Ｒ²は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、ｂは２以上の整数であり、ｃは０以上の整数であり、ｄは０以上の整数であり、ｅは０以上の整数であり、及び２≦ｂ＋ｃ＋ｄ＋ｅ≦５０である。ただし、前記Ｒ¹及びＲ²のうち少なくとも２個はアルケニル基である。） The production method of the present invention is characterized by blending (a1) a cyclic organopolysiloxane represented by the following general formula (1) and (a2) a linear or branched organopolysiloxane represented by the following average composition formula (2) in a specific ratio, and (a3) polymerizing them in the presence of a cation exchange resin that is substantially free of water for a reaction time of 60 minutes or less.

(In the formula, ^R1 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is an integer satisfying 3≦a≦6.)

(In the formula, R ² 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, b is an integer of 2 or more, c is an integer of 0 or more, d is an integer of 0 or more, e is an integer of 0 or more, and 2≦b+c+d+e≦50, with the proviso that at least two of R ¹ and R ² are alkenyl groups.)

（式中、Ｒ¹は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、ａは３≦ａ≦６を満たす整数である。） [Component (a1)]
The component (a1) is a cyclic organopolysiloxane represented by the following general formula (1).

(In the formula, ^R1 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is an integer satisfying 3≦a≦6.)

In the above formula (1), R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, such as alkyl groups such as methyl, ethyl, propyl, butyl, and octyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl, in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine, fluorine, and bromine. R ¹ is preferably an alkyl group or an alkenyl group, more preferably a methyl group or a vinyl group, and from the viewpoint of compatibility with component (a2), it is preferable that 70 mol % or more of all R ^1s are methyl groups.

In the above formula (1), a is an integer that satisfies 3≦a≦6, and preferably an integer that satisfies 3≦a≦5. If a is greater than 6, the reactivity of component (a1) decreases, and it may not be possible to obtain an alkenyl group-containing organopolysiloxane having the desired structure.

Examples of the cyclic organopolysiloxane of the above formula (1) include dimethylsiloxane cyclic compounds such as hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane, methylvinylsiloxane cyclic compounds such as tetramethyltetravinylcyclotetrasiloxane, diphenylsiloxane cyclic compounds such as octaphenylcyclotetrasiloxane, methyltrifluoropropylsiloxane cyclic compounds such as trimethyltrifluoropropylcyclotrisiloxane, etc. Among these, from the viewpoint of ease of raw material procurement, dimethylsiloxane cyclic compounds such as octamethylcyclotetrasiloxane are preferred, and from the viewpoint of introduction of alkenyl groups as crosslinking points, the combined use of methylvinylsiloxane cyclic compounds is preferred.
These cyclic organopolysiloxanes may be used alone or in combination of two or more.

（式中、Ｒ²は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、ｂは２以上の整数であり、ｃは０以上の整数であり、ｄは０以上の整数であり、ｅは０以上の整数であり、及び２≦ｂ＋ｃ＋ｄ＋ｅ≦５０である。ただし、前記Ｒ¹及びＲ²のうち少なくとも２個はアルケニル基である。） [Component (a2)]
Component (a2) is a linear or branched organopolysiloxane represented by the following average composition formula (2): Component (a2) is an end-capping agent that is added to adjust the degree of polymerization by terminating the polymerization reaction.

(In the formula, R ² 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, b is an integer of 2 or more, c is an integer of 0 or more, d is an integer of 0 or more, e is an integer of 0 or more, and 2≦b+c+d+e≦50, with the proviso that at least two of R ¹ and R ² are alkenyl groups.)

In the above formula (2), examples of the monovalent hydrocarbon group represented by ^R2 include the monovalent hydrocarbon groups exemplified for the above component (a1), of which methyl or vinyl groups are preferred, and it is preferable that 70 mol% or more of all ^R2 are methyl groups. If the proportion of methyl groups is less than 70 mol% of all ^R2 , the compatibility with the above component (a1) is poor, and the mixture of components (a1) and (a2) may become cloudy and separate, which may result in poor production.
In formula (1) of component (a1) and formula (2) of component (a2) above, at least two of R ¹ and R ² are alkenyl groups, and preferably from 2 to 20. The alkenyl group may be in either R ¹ or R ² , but in order to obtain an organopolysiloxane having an alkenyl group at its terminal, it is preferable that at least one of the R ² in the R ² _{3SiO 1/2} unit (M unit) in formula (2) above is an alkenyl group.

In the above formula (2), b is an integer of 2 or more, preferably an integer of 2 to 15, c is an integer of 0 or more, preferably an integer of 0 to 20, d is an integer of 0 or more, preferably an integer of 0 to 15, e is an integer of 0 or more, preferably an integer of 0 to 10, and 2≦b+c+d+e≦50, preferably 2≦b+c+d+e≦40, more preferably 2≦b+c+d+e≦30. If b+c+d+e exceeds the above upper limit, the reactivity as a terminal blocking agent decreases, and the desired alkenyl group-containing organopolysiloxane cannot be obtained.

Examples of linear or branched organopolysiloxanes represented by the average composition formula (2) include, but are not limited to, compounds represented by the following structures. In the following formula, Me and Vi represent a methyl group and a vinyl group, respectively (the same applies below). The bonding order of each siloxane unit shown in parentheses is not limited to the following. These linear or branched organopolysiloxanes may be used alone or in combination of two or more types.

（０≦ｚ１≦４８）

（０≦ｚ２≦４８）

（０≦ｚ３≦４６、２≦ｚ４≦４８、２≦ｚ３＋ｚ４≦４８）

（０≦ｚ５≦４７、１≦ｚ６≦４８、１≦ｚ５＋ｚ６≦４８）

（０≦ｚ７≦４６、０≦ｚ８≦４６、１≦ｚ９≦２４、２≦ｚ７＋（（ｚ８＋２）×ｚ９）≦４８）

（０≦ｚ１０≦４５、０≦ｚ１１≦４３、０≦ｚ１２≦２２、０≦ｚ１３≦４５、０≦ｚ１４≦４５、１≦ｚ１５≦１６、３≦ｚ１０＋（（ｚ１１＋２）×ｚ１２）＋（（ｚ１３＋ｚ１４＋３）×ｚ１５）≦４８）

(0≦z1≦48)

(0≦z2≦48)

(0≦z3≦46, 2≦z4≦48, 2≦z3+z4≦48)

(0≦z5≦47, 1≦z6≦48, 1≦z5+z6≦48)

(0≦z7≦46, 0≦z8≦46, 1≦z9≦24, 2≦z7+((z8+2)×z9)≦48)

(0≦z10≦45, 0≦z11≦43, 0≦z12≦22, 0≦z13≦45, 0≦z14≦45, 1≦z15≦16, 3≦z10+((z11+2)×z12)+((z13+z14+3)×z15)≦48)

The compounding ratio of components (a1) and (a2) used in the present invention can be changed depending on the desired degree of polymerization of the alkenyl group-containing organopolysiloxane, but the molar ratio of R ¹ ₂ SiO _2/2 units (D units) in component (a1) to component (a2) is preferably 1:1 to 498:1, more preferably 2:1 to 400:1, and even more preferably 3:1 to 300:1. If the amount of component (a2) is too small, the end group may be insufficient, resulting in a high viscosity, whereas if the amount is too large, the end group may be excessive, resulting in a low viscosity.

[Component (a3)]
The component (a3) is a cation exchange resin that acts as a catalyst to polymerize the components (a1) and (a2). The cation exchange resin used in the present invention is preferably a dry type, which has a water content of 1.6 mass% or less and is substantially free of water. If a cation exchange resin other than this is used, the performance as a catalyst is inferior, and the alkenyl-containing organopolysiloxane with the desired polymerization degree is not obtained.

The cation exchange resin of the present invention is preferably a styrene-divinylbenzenesulfonic acid copolymer having a skeleton formed by copolymerizing styrene and divinylbenzene, but a microporous cation exchange resin in which the sulfonic groups bonded to the phenyl groups in the skeleton are in the H ⁺ type is more preferable.

Such cation exchange resins are commercially available, for example, Amberlyst 15JS-HG DRY (manufactured by Organo Corporation, styrene-divinylbenzenesulfonic acid copolymer, microporous type, moisture content of 1.6% by mass or less), Duolite SC100 (manufactured by Sumitomo Chemical CHEMTEX, styrene-divinylbenzenesulfonic acid copolymer, microporous type, moisture content of 1.5% by mass or less), etc.

[Production method]
The method for producing the alkenyl-containing organopolysiloxane using the cation exchange resin of component (a3) above can be either a batch system or a continuous system.

In the case of a batch-type production method , the cation exchange resin (a3) is added to a mixture of the components (a1) and (a2) and reacted at a predetermined temperature for a predetermined time. The cation exchange resin is then filtered, neutralized, and unreacted low molecular weight siloxanes and the like are removed under heating and reduced pressure (stripping step), whereby an alkenyl group-containing organopolysiloxane can be easily obtained.

Here, the amount of cation exchange resin added in the case of a batch system is preferably 0.001 to 30% by mass, more preferably 0.01 to 20% by mass, and even more preferably 0.1 to 10% by mass, based on the total amount of the (a1) and (a2) components. If the amount of cation exchange resin used is less than the lower limit, polymerization may be insufficient, and if it exceeds the upper limit, siloxane may be adsorbed, leading to a decrease in yield, etc.

In the case of a batch system, the reaction temperature is preferably 0 to 150°C, more preferably 25 to 125°C, and even more preferably 50 to 100°C, and the reaction time is preferably within 60 minutes, more preferably 1 to 60 minutes, and even more preferably 5 to 50 minutes. If the reaction temperature is below the lower limit, polymerization may be insufficient, and if it exceeds the upper limit, there is a risk of causing deterioration of the cation exchange resin, which is not preferable. If the reaction time is below the lower limit, polymerization may be insufficient, and if it exceeds the upper limit, the reaction does not proceed any further, which is inefficient.

Various methods are known for the batch neutralization process, and one of the simplest methods is to treat the polymer of the (a1) and (a2) components with hydrotalcites. Hydrotalcites are compounds containing magnesium and aluminum with a layered structure, and examples of such compounds include Kyoward 300, 500SH, and 1000 (manufactured by Kyowa Chemical Industry Co., Ltd.). The amount added is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.8 parts by mass, and even more preferably 0.1 to 0.6 parts by mass, per 100 parts by mass of the polymer. If the amount added is less than the lower limit, it may be difficult to sufficiently remove the acid catalyst eluted from the (a3) component remaining in the polymer, and if the amount added exceeds the upper limit, the amount of ionic impurities such as magnesium ions and aluminum ions increases, which is not preferable. The conditions for treating with hydrotalcites are not limited since they vary depending on the viscosity of the polymer and the amount of impurities, but the treatment temperature is generally 0 to 80° C., preferably 20 to 60° C., and the treatment time is generally 1 to 5 hours, preferably 1 to 3 hours. After the treatment, the hydrotalcites can be removed by filtration.

The batch-type stripping process is carried out by placing the polymer of the (a1) and (a2) components after neutralization by the above method in a flask or the like, and stripping unreacted low molecular weight siloxanes, etc. at any temperature and time. In this case, the temperature is preferably 50 to 200°C, more preferably 80 to 180°C, and the time is preferably 0.5 to 10 hours, more preferably 1 to 8 hours. If the stripping temperature and time are less than the above lower limit, the stripping is insufficient, and unreacted low molecular weight siloxanes, etc. may remain. If the stripping temperature and time exceed the above upper limit, the functional groups of the polymer may be removed or the main chain may be cut, and the desired organopolysiloxane may not be obtained. If necessary, stripping may be carried out under reduced pressure, in which case the pressure is 50 mmHg or less, preferably 30 mmHg.

As described above, the production of alkenyl-containing organopolysiloxane using a cation exchange resin can be carried out in a batch system, but a continuous system is preferred as a method with higher productivity and lower cost. In the continuous system, the mixture of components (a1) and (a2) is continuously passed through a column (e.g., a cylindrical column) packed with a cation exchange resin to carry out polymerization.

Here, the amount of cation exchange resin (a3) used in the case of a continuous system should be an amount that fills about 80% of the volume of the column to be packed. If the amount used is too small, polymerization may be insufficient, and if the amount used is too large, the cation exchange resin may become wet and expand during use, leading to damage to the column.

In this case, the reaction conditions such as residence time and temperature can be appropriately determined based on the reactivity of the raw materials used (the above-mentioned components (a1) and (a2)) and the cation exchange resin catalyst. Generally, similar to the reaction conditions for the batch method described above, the reaction temperature is preferably 0 to 150°C, more preferably 25 to 125°C, and even more preferably 50 to 100°C, and the residence time is preferably within 60 minutes, more preferably 1 to 60 minutes, and even more preferably 5 to 50 minutes. In the continuous method, there is no filtration of the cation exchange resin after polymerization, making it possible to produce products with higher productivity than the batch method.

Furthermore, in the case of the continuous type, the following steps (neutralization and stripping) are also performed continuously. That is, in the neutralization step, the polymer of the (a1) component and the (a2) component is continuously passed through a column (for example, a cylindrical column such as a cylindrical column) filled with an ion exchange resin for neutralization, thereby performing neutralization. As the ion exchange resin, it is preferable to use an ion exchange resin obtained by mixing a cation exchange resin and an anion exchange resin, and examples of such an ion exchange resin include Duolite UP6000, Duolite UP7000, Sumikaion MB77 (all manufactured by Sumitomo Chemical Chemtex Co., Ltd.), and Amberlyst MSPS2-1.DRY (manufactured by Organo Corporation). Here again, since filtration of neutralizing agents such as neutralizing salts and hydrotalcites is not required, highly productive production is possible.
The amount of the ion exchange resin used for neutralization should be such that it fills about 80% of the volume of the column it is packed in. If the amount used is too small, neutralization may be insufficient, whereas if the amount used is too large, the ion exchange resin used for neutralization may become wet and expand during use, which may lead to damage to the column.
The temperature in the neutralization step is preferably 0 to 120° C., more preferably 30 to 100° C., and even more preferably 50 to 80° C., and the residence time is preferably within 60 minutes, more preferably 1 to 60 minutes, and even more preferably 5 to 50 minutes.

An example of a continuous stripping step is short path distillation using a thin film distillation apparatus. The thin film distillation apparatus may be a known apparatus equipped with an agitation drive device for dispersing the polymer of the (a1) and (a2) components in a thin film, and a heating and evaporation/concentration section for heating the polymer thin layer under reduced pressure to evaporate and concentrate. In any of such apparatuses, the distillation operation can be performed by a method normally used for the operation of the apparatus. Specifically, the temperature in the thin film distillation is preferably 100 to 280°C, more preferably 150 to 250°C. If the temperature is less than the lower limit, unreacted low molecular weight siloxanes and the like may not be sufficiently distilled off, which may lead to a decrease in the purity of the final product, which is not preferable. In addition, if the temperature exceeds the upper limit, the polymer may become highly viscous or gel. The pressure in the thin film distillation can be changed arbitrarily, but is preferably 1×10 ^-7 to 5 mmHg, more preferably 1×10 ^-6 to 3 mmHg. If the pressure is less than the lower limit, the boiling point difference between the target of the polymer and unreacted low molecular weight siloxanes, etc., is reduced, and the target may be distilled off, which may lead to a decrease in the purity of the final product, which is not preferable. If the pressure exceeds the upper limit, the unreacted low molecular weight siloxanes, etc. may not be sufficiently distilled off, which may lead to a decrease in the purity of the final product. Furthermore, the feed rate is also an important factor in thin film distillation, and is preferably 0.1 to 10 g/min, more preferably 1 to 5 g/min. If the feed rate is less than the lower limit, the efficiency of reduced pressure distillation decreases, which is industrially disadvantageous, and is not preferable. If the pressure exceeds the upper limit, the separation efficiency may deteriorate, which may lead to a decrease in the purity of the final product.

（式中、Ｒ³は互いに独立に、非置換又は置換の炭素原子数１～１２の一価炭化水素基であり、Ｒ³のうち少なくとも２個はアルケニル基であり、ｆは２以上の整数であり、ｇは３以上の整数であり、ｈは０以上の整数であり、ｉは０以上の整数であり、及び１０≦ｆ＋ｇ＋ｈ＋ｉ≦５００である。） [Product]
As described above, the alkenyl-containing organopolysiloxane obtained by the production method of the present invention is represented by the following average composition formula (3): The alkenyl-containing organopolysiloxane may be used alone or in combination of two or more kinds.

(In the formula, R3 ^'s are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, at least two of the ^R3 's are alkenyl groups, f is an integer of 2 or greater, g is an integer of 3 or greater, h is an integer of 0 or greater, i is an integer of 0 or greater, and 10≦f+g+h+i≦500.)

In the above formula (3), examples of the monovalent hydrocarbon group represented by ^R3 include the monovalent hydrocarbon groups exemplified as ^R1 in the above general formula (1). Among these, a methyl group or a vinyl group is preferred, and it is preferred that 70 mol % or more of all ^R3s are methyl groups in view of good curability.
At least two of ^R3 are alkenyl groups, and if there are less than two, there is a high possibility that uncrosslinked molecules remain after curing, which is undesirable because the curability is reduced. More specifically, the content of alkenyl groups is preferably 0.001 mol or more and less than 1 mol, more preferably 0.005 mol or more and 0.8 mol or less, and even more preferably 0.01 mol or more and 0.6 mol or less per 100g of the alkenyl group-containing organopolysiloxane. If it exceeds the upper limit, the alkenyl groups become excessive, which is undesirable because the curability is reduced.

The viscosity of the alkenyl-containing organopolysiloxane at 25°C is 1 to 1,000 mPa·s, preferably 3 to 900 mPa·s, and more preferably 5 to 800 mPa·s. As will be described in detail later, the alkenyl-containing organopolysiloxane can be used together with an organohydrogenpolysiloxane and a platinum group metal catalyst to provide a curable organopolysiloxane composition. Furthermore, the composition can be applied to at least one surface of a sheet-like substrate, and a release sheet having a layer made of a cured product of the composition can be provided by heat curing. In this way, when the alkenyl-containing organopolysiloxane is used as the main agent of the composition, the above viscosity is preferable from the viewpoint of coatability. In both cases where the viscosity exceeds the upper limit value and is less than the lower limit value, the coatability of the composition may decrease, which is not preferable. In the present invention, the viscosity can be measured using a B-type viscometer (for example, "TVB-10M" manufactured by Toki Sangyo Co., Ltd.). The rotor and rotation speed are appropriately selected depending on the viscosity. For example, if the viscosity is about 500 mPa · s, the measurement can be performed with a TM3 rotor at a rotation speed of 60 rpm (same below).

In the above formula (3), f is an integer of 2 or more, preferably an integer of 2 to 15, g is an integer of 3 or more, preferably an integer of 8 to 498, h is an integer of 0 or more, preferably an integer of 0 to 15, i is an integer of 0 or more, preferably an integer of 0 to 10, and 10≦f+g+h+i≦500, preferably 10≦f+g+h+i≦400, and more preferably 10≦f+g+h+i≦300. When f+g+h+i exceeds the above upper limit or is less than the above lower limit, as described above, when the alkenyl group-containing organopolysiloxane is used as the main agent of a curable organopolysiloxane composition, the coatability of the composition decreases.
Here, f+g+h+i is greater than the value of b+c+d+e of the linear or branched organopolysiloxane represented by formula (2) used in the production of the alkenyl-containing organopolysiloxane represented by formula (3).

Examples of alkenyl group-containing organopolysiloxanes obtained by the manufacturing method of the present invention include, but are not limited to, the following. The bonding order of each siloxane unit shown in parentheses is not limited to the following.

（８≦ｚ１６≦４９８）

（８≦ｚ１７≦４９８）

（０≦ｚ１８≦４９６、２≦ｚ１９≦４９８、８≦ｚ１８＋ｚ１９≦４９８）

（０≦ｚ２０≦４９７、１≦ｚ２１≦４９８、８≦ｚ２０＋ｚ２１≦４９８）

（０≦ｚ２２≦４９６、０≦ｚ２３≦４９６、１≦ｚ２４≦２４９、８≦ｚ２２＋（（ｚ２３＋２）×ｚ２４）≦４９８）

（０≦ｚ２５≦４９５、０≦ｚ２６≦４９３、０≦ｚ２７≦２４７、０≦ｚ２８≦４９５、０≦ｚ２９≦４９５、１≦ｚ３０≦１６６、８≦ｚ２５＋（（ｚ２６＋２）×ｚ２７）＋（（ｚ２８＋ｚ２９＋３）×ｚ３０）≦４９８）

(8≦z16≦498)

(8≦z17≦498)

(0≦z18≦496, 2≦z19≦498, 8≦z18+z19≦498)

(0≦z20≦497, 1≦z21≦498, 8≦z20+z21≦498)

(0≦z22≦496, 0≦z23≦496, 1≦z24≦249, 8≦z22+((z23+2)×z24)≦498)

(0≦z25≦495, 0≦z26≦493, 0≦z27≦247, 0≦z28≦495, 0≦z29≦495, 1≦z30≦166, 8≦z25+((z26+2)×z27)+((z28+z29+3)×z30)≦498)

[Curable organopolysiloxane composition]
The present invention further provides a curable organopolysiloxane composition comprising an alkenyl-containing organopolysiloxane (A) represented by the above average composition formula (3) obtained by the above production method, an organohydrogenpolysiloxane (B) having at least two hydrogen atoms bonded to silicon atoms in each molecule, and a platinum group metal catalyst (C). It is also possible to provide a release sheet having a sheet-like substrate and a layer made of a cured product of the composition on at least one surface of the substrate.

[Component (B)]
Component (B) is an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms (hereinafter referred to as SiH groups) in each molecule, and may be any of the known organohydrogenpolysiloxanes used in addition reaction type organopolysiloxane compositions. The organohydrogenpolysiloxanes may be used alone or in combination of two or more.

The SiH groups in the organohydrogenpolysiloxane of component (B) and the alkenyl groups in component (A) undergo an addition reaction to harden and form a coating.
The organohydrogenpolysiloxane of the component (B) is represented, for example, by the following average composition formula (4).
^R4jHkSiO _{( 4-jk)/2} ... ( ₄ )
(In the formula, R4 ^'s are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, excluding aliphatic unsaturated hydrocarbon groups, with the proviso that at least 50 mol% of all ^R4 's are methyl groups, and j and k are positive numbers satisfying 0.7≦j≦2.1, 0.001≦k≦1.0, and 0.8≦j+k≦3.0. The organohydrogenpolysiloxane has at least two hydrogen atoms bonded to silicon atoms in each molecule.)

In the above formula (4), R ⁴ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, excluding aliphatic unsaturated hydrocarbon groups, and examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, and octyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; or monovalent hydrocarbon groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with hydroxyl groups, cyano groups, halogen atoms, alkoxysilyl groups, polyoxyalkylene groups, epoxy groups, carboxyl groups, etc. R ⁴ is preferably an alkyl group, more preferably a methyl group, and from the viewpoint of low curability and peel strength, it is preferable that 50 mol % or more, typically 60 to 100 mol %, of all R ^4s are methyl groups. If the proportion of methyl groups is less than 50 mol % of all R ⁴ groups, then compatibility with component (A) will be poor, and the curable organopolysiloxane composition may become cloudy or undergo phase separation.

In the above formula (4), j is a positive number satisfying 0.7≦j≦2.1, preferably 1.0≦j≦2.0, k is a positive number satisfying 0.001≦k≦1.0, preferably 0.01≦k≦0.98, and j+k is a positive number satisfying 0.8≦j+k≦3.0, preferably 1.3≦j+k≦2.5.

The organohydrogenpolysiloxane of the component (B) may be linear, branched, or cyclic, or may be a mixture thereof. Examples of the organohydrogenpolysiloxane include polymers or copolymers having at least one of ^R4HSiO2 _/2 unit, HSiO3 _/2 unit, and R42HSiO1 _/2 unit, and optionally further having at least one of ^R42SiO2 _{/ 2} unit, _{R4SiO3 /2} unit, and ^R43SiO1 _{/ 2} unit. ^R4 is as described above. It is preferable that ^the total number of ^R4HSiO2 _{/2 unit} or ^R42HSiO1 _/ 2 unit is at least two in one molecule. In addition, ^SiO4 _/2 unit may be contained, and the amount may be within a range that does not impair the effect of the present invention.

The content of SiH groups in one molecule of the organohydrogenpolysiloxane is 2 to 300, preferably 3 to 200, and more preferably 5 to 100. If the number of SiH groups is less than the above lower limit or exceeds the above upper limit, the curability or adhesion may decrease.
The organohydrogenpolysiloxane of component (B) preferably has 2 to 502 silicon atoms (or a degree of polymerization) per molecule, and more preferably has about 10 to 100 silicon atoms.

The viscosity of component (B) at 25°C is preferably 0.1 to 5,000 mPa·s, more preferably 0.3 to 3,000 mPa·s, and even more preferably 0.5 to 1,000 mPa·s. If the viscosity is too low, curability may decrease, and if it is too high, coatability may decrease.

（２≦ｚ３１≦３００）

（２≦ｚ３２≦３００、１≦ｚ３３≦４９８、２≦ｚ３２＋ｚ３３≦５００）

（０≦ｚ３４≦２９８、０≦ｚ３５≦５００、０≦ｚ３４＋ｚ３５≦５００）

（０≦ｚ３６≦３００、０≦ｚ３７≦３００、１≦ｚ３８≦２４８、２≦ｚ３６＋ｚ３７≦３００、２≦ｚ３６＋（（ｚ３７＋２）×ｚ３８）≦５００）

（０≦ｚ３９≦３００、０≦ｚ４０≦３００、０≦ｚ４１≦２４６、０≦ｚ４２≦３００、０≦ｚ４３≦３００、１≦ｚ４４≦１６５、２≦ｚ３９＋ｚ４０＋ｚ４２＋ｚ４３≦３００、２≦ｚ３９＋（（ｚ４０＋２）×ｚ４１）＋（（ｚ４２＋ｚ４３＋３）×ｚ４４）≦５００） Examples of component (B) include, but are not limited to, the following compounds: The bonding order of the siloxane units shown in parentheses is not limited to the following.

(2≦z31≦300)

(2≦z32≦300, 1≦z33≦498, 2≦z32+z33≦500)

(0≦z34≦298, 0≦z35≦500, 0≦z34+z35≦500)

(0≦z36≦300, 0≦z37≦300, 1≦z38≦248, 2≦z36+z37≦300, 2≦z36+((z37+2)×z38)≦500)

(0≦z39≦300, 0≦z40≦300, 0≦z41≦246, 0≦z42≦300, 0≦z43≦300, 1≦z44≦165, 2≦z39+z40+z42+z43≦300, 2≦z39+((z40+2)×z41)+((z42+z43+3)×z44)≦500)

The amount of component (B) is such that the ratio of the number of SiH groups in component (B) to the number of alkenyl groups in component (A) is preferably 0.5 to 5, more preferably 0.7 to 4, and even more preferably 1 to 3. If the ratio is less than the lower limit, the adhesion between the cured coating and the substrate may decrease. If it is greater than the upper limit, the resulting release sheet may become difficult to release (i.e., a strong force is required to peel the adhesive material from the release sheet), and the adhesive strength (residual adhesive strength) remaining in the adhesive material after peeling may decrease.

[Component (C)]
The component (C) is a platinum group metal catalyst for promoting the addition reaction with the above-mentioned components (A) and (B). Any catalyst that promotes the so-called hydrosilylation reaction can be used, and any known catalyst can be used. Examples of platinum group metal catalysts include platinum, palladium, rhodium, and ruthenium catalysts, and among these, platinum catalysts are particularly preferred. Examples of the platinum catalyst include chloroplatinic acid, alcoholic or aldehyde solutions of chloroplatinic acid, and complexes of chloroplatinic acid or platinum with various olefins or vinylsiloxanes.

The amount of component (C) used should be a catalytic amount. A catalytic amount is an effective amount that can promote the above-mentioned addition reaction. In order to obtain a good cured film and from an economical standpoint, it is preferable that the mass of the platinum group metal be 10 to 200 ppm relative to the total mass of the curable organopolysiloxane composition, particularly the combined mass of components (A) and (B). The platinum group metal catalyst may be used alone or in combination of two or more types.

[Other ingredients]
In addition to the above components (A) to (C), any other components may be blended into the curable organopolysiloxane composition. For example, the following components may be mentioned. Each of the other components may be used alone or in combination of two or more.

Pot life extender The curable organopolysiloxane composition of the present invention may further contain (D) a pot life extender in order to ensure the pot life. The pot life extender is not particularly limited as long as it is a compound that has a curing inhibitory effect on the platinum group metal catalyst of the above component (C), and conventionally known compounds may be used. For example, various organic nitrogen compounds, organic phosphorus compounds, acetylene compounds, oxime compounds, and organic chloro compounds may be mentioned.

More specifically, for example, acetylene alcohols such as 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-pentyn-3-ol, 2-phenyl-3-butyn-2-ol, and 1-ethynylcyclohexanol, acetylene compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne, reaction products of these acetylene compounds with alkoxysilanes, siloxanes, or hydrogensilanes, vinyl siloxanes such as tetramethylvinylsiloxane cyclics, organic nitrogen compounds such as benzotriazole, and other organic phosphorus compounds, oxime compounds, and organic chloro compounds can be included. The amount of these compounds to be blended may be any amount that provides a good pot life. In general, 0.01 to 10 parts by mass is preferable, and more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the total of the (A) and (B) components. By adding an appropriate amount of the pot life extender, the release agent composition becomes more excellent in long-term storage stability at room temperature and heat curing properties.

Alkenyl-containing compounds other than component (A) In addition to component (A), the composition of the present invention may also contain an alkenyl-containing compound that undergoes addition reaction with component (B).As the alkenyl-containing compound other than component (A), it is preferable that it is involved in the formation of a cured product, and an organopolysiloxane having one alkenyl group per molecule can be mentioned.The molecular structure of the compound may be, for example, linear, cyclic, branched, or three-dimensional network.

Furthermore, it is also possible to blend alkenyl-containing organic compounds other than the above organopolysiloxanes. For example, monomers such as diacrylates derived from α-olefins, butadiene, and polyfunctional alcohols; polyolefins such as copolymers of polyethylene, polypropylene, or styrene with other ethylenically unsaturated compounds (e.g., acrylonitrile or butadiene); oligomers or polymers derived from functionally substituted organic compounds such as esters of acrylic acid, methacrylic acid, or maleic acid. These alkenyl-containing compounds may be liquid or solid at room temperature.

Other optional components Furthermore, known antioxidants, pigments, stabilizers, antistatic agents, defoamers, adhesion improvers, thickeners, or inorganic fillers such as silica may be blended as necessary within the range that does not impair the effects of the present invention. The blending amount may be appropriately selected according to conventional techniques.

[Method for producing curable organopolysiloxane composition]
The curable organopolysiloxane composition of the present invention can be obtained by mixing the above-mentioned components (A), (B), and (C), and, if necessary, a pot life extender and/or optional components, in their respective prescribed amounts. From the standpoint of pot life, it is preferable to mix the above-mentioned components (A), (B), and optional components uniformly in advance, and then add the platinum group metal catalyst (C) immediately before use.

The curable organopolysiloxane composition of the present invention preferably has a viscosity at 25° C. of 50 to 1,000 mPa·s, more preferably 80 to 800 mPa·s, and even more preferably 100 to 600 mPa·s. If the viscosity is outside the above range, problems may arise such as the inability to coat a cured coating on a substrate, or even if coating is possible, the coating may not be uniform.
The curable organopolysiloxane composition of the present invention has a low viscosity and does not require a solvent, and therefore can be made into a solventless curable organopolysiloxane composition.

[Coated product (release sheet)]
The present invention further provides a release sheet having a sheet-like substrate and a cured coating of the above-mentioned curable organopolysiloxane composition on one or both surfaces of the substrate, the cured coating being formed by coating the above-mentioned curable organopolysiloxane composition on one or both surfaces of the substrate and heating.

The coating method and heat curing conditions are not particularly limited and may be selected appropriately, but for example, the curable organopolysiloxane composition can be applied directly to one or both sides of a sheet-like substrate such as paper or film at 0.01 to 100 g/m 2 using a coating method such as coating with a comma coater, lip coater, roll coater, die coater, knife coater, blade coater, rod coater, kiss coater, gravure coater, wire bar coater, screen coating, dip coating, cast coating, or the ^like , and then heated at 50 to 200° C. for 1 to 120 seconds to form a cured coating on the substrate. When forming release layers on both sides of the substrate, it is preferable to perform the operation of forming a cured coating on each side of the substrate at a time.

In the present invention, the release sheet includes not only those in which the sheet-like substrate is paper, but also those formed from various known films. Examples of substrates include polyethylene laminated paper, glassine paper, fine paper, craft paper, various coated papers such as clay-coated paper, synthetic paper such as Yupo, polyethylene film, polypropylene film such as CPP and OPP, polyester film such as polyethylene terephthalate film, polyamide film, polyimide film, polylactic acid film, polyphenol film, polycarbonate film, etc. It is also possible to use process paper for manufacturing artificial leather, ceramic sheets, double-sided separators, etc. as the substrate. In order to improve the adhesion between these substrates and the release layer, the substrate surface may be corona-treated, etched, primer-treated, or plasma-treated.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.
The weight average molecular weights listed below were determined by gel permeation chromatography (GPC) analysis (solvent: toluene, polystyrene equivalent), and the viscosities were measured using a rotational viscometer at 25°C. The volatile content (unreacted low molecular weight siloxanes, etc.) measured during the reaction was calculated from the remaining amount of the reactants after placing about 1.5 g of the reactants in an aluminum dish with a diameter of 6 cm and heating at 150°C for 30 minutes in an open system. The vinyl group content was measured by a method conforming to the iodine value measurement method described in JIS K0070. The structure of each alkenyl group-containing organopolysiloxane was determined by ^29Si -NMR.

The following raw materials were used in the examples and comparative examples: In the following formulae, Me is a methyl group, and Vi is a vinyl group.
Component (a1) (a1-1) Octamethylcyclotetrasiloxane (a1-2) Tetramethyltetravinylcyclotetrasiloxane

（ａ２－３）下記式で表される分岐状オルガノポリシロキサン

Component (a2) (a2-1) Tetramethyldivinyldisiloxane (a2-2) Linear organopolysiloxane represented by the following formula:

(a2-3) A branched organopolysiloxane represented by the following formula:

Component (a3) (a3-1) Cation exchange resin Amberlyst 15JS-HG DRY manufactured by Organo Corporation
Microporous type, moisture content 1.6% by mass or less (a3-2) Cation exchange resin Duolite SC100 manufactured by Sumitomo Chemical Chemtex Co., Ltd.
Microporous type, moisture content 1.5% or less by mass

（ａ４－２）オルガノ社製陽イオン交換樹脂アンバーリスト３１ＷＥＴ
ゲル型、水分含有率６３～６７質量％ Component (a4): Comparative Example Component (a4-1) Linear organopolysiloxane represented by the following formula:

(a4-2) Organo Corporation cation exchange resin Amberlyst 31WET
Gel type, moisture content 63-67% by weight

Preparation of Alkenyl Group-Containing Organopolysiloxane [Example 1]
A 300 ml separable flask equipped with a thermometer and stirring blade and purged with nitrogen was charged with (a1-1) 149.8 g of octamethylcyclotetrasiloxane (2.0 mol of D units (Me ₂ SiO _2/2 units, Me is a methyl group)), (a2-1) 3.7 g (0.02 mol) of tetramethyldivinyldisiloxane, and (a3-1) 15.4 g (10% by mass relative to the total amount of (a1-1) and (a2-1)) of cation exchange resin Amberlyst 15JS-HG DRY manufactured by Organo Corporation, and heated with stirring at 80° C. for 30 minutes. A portion of the reaction mixture was withdrawn and the volatile content was measured, which was 12% by mass, confirming that the reaction had progressed. The reaction mixture was filtered to remove the cation exchange resin, and then 0.55 g (3,600 ppm relative to the total amount of (a1-1) and (a2-1)) of Kyoward 500SH manufactured by Kyowa Chemical Industry Co., Ltd. was added, followed by heating and stirring at 50°C for 2 hours (neutralization step). After removing the Kyoward 500SH by filtration, the reaction mixture was placed in a separable flask and subjected to reduced pressure stripping at 150°C and 5 mmHg for 3 hours to obtain an alkenyl group-containing organopolysiloxane (A-1) represented by the following average composition formula and having a viscosity of 190 mPa·s at 25°C. The weight average molecular weight was 12,600, and the proportion of vinyl groups was 0.026 mol/100g (theoretical value 0.026 mol/100g).
(A-1)

[Example 2]
A cylindrical column having an inner diameter of 22 mm and a length of 120 mm was filled with (a3-1) cation exchange resin Amberlyst 15JS-HG DRY manufactured by Organo Corporation to about 80% of the internal volume, and then a mixed liquid of 97.58 mass% of (a1-1) octamethylcyclotetrasiloxane and 2.42 mass% of (a2-1) tetramethyldivinyldisiloxane (molar ratio: D units in (a1-1)/(a2-1)=100) was continuously passed through the column so that the polymerization temperature was 80° C. and the residence time was 20 minutes. A portion of the reaction product was withdrawn and the volatile content was measured, which was 12 mass%, confirming that the reaction had progressed. Further, a cylindrical column with an inner diameter of 22 mm and a length of 120 mm was filled with Organo Corporation's ion exchange resin Amberlyst MSPS2-1.DRY to about 80% of the internal volume, and the polymer was continuously passed therethrough so that the neutralization temperature was 50°C and the residence time was 20 minutes to carry out neutralization. The neutralized polymer was continuously stripped using a thin film distillation apparatus (Shibata Scientific MS-300 type, rotary thin film distillation apparatus) at a temperature of 150°C, a pressure of 0.30 mmHg, and a feed rate of 2.0 g/min to obtain an alkenyl group-containing organopolysiloxane (A-2) represented by the following average composition formula having a viscosity of 190 mPa·s at 25°C. The weight average molecular weight was 11,800, and the proportion of vinyl groups was 0.026 mol/100g (theoretical value 0.026 mol/100g).
(A-2)

[Examples 3 to 7]
Alkenyl-containing organopolysiloxanes (A-3) to (A-7) were obtained in accordance with the synthesis example of Example 2, except that the raw materials used in Example 2 were changed to those listed in Table 1 below. The structure of the average composition of each is shown in the formula below. The physical properties of the obtained alkenyl-containing organopolysiloxanes are summarized in Table 1. The D unit in (a1-2) is a MeViSiO2 _/2 unit (Me is a methyl group, and Vi is a vinyl group).

（Ａ－４）

（Ａ－５）

（Ａ－６）

（Ａ－７）

(A-3)

(A-4)

(A-5)

(A-6)

(A-7)

[Comparative Example 1]
A cylindrical column having an inner diameter of 22 mm and a length of 120 mm was filled with (a3-1) cation exchange resin Amberlyst 15JS-HG DRY manufactured by Organo Corporation to about 80% of the internal volume, and then a mixed liquid of 29.26 mass% of (a1-1) octamethylcyclotetrasiloxane and 70.74 mass% of (a4-1) linear organopolysiloxane (molar ratio of D units in (a1-1)/(a4-1)=30) was continuously passed through the column so that the polymerization temperature was 80° C. and the residence time was 20 minutes. However, when a portion of the reaction product was extracted and the volatile content was measured, it was found to be 34 mass%, indicating that the reaction had not progressed sufficiently.

[Comparative Example 2]
A cylindrical column having an inner diameter of 22 mm and a length of 120 mm was filled with (a4-2) cation exchange resin Amberlyst 31WET manufactured by Organo Corporation to about 80% of the internal volume, and then a mixed liquid containing 97.58 mass% of (a1-1) octamethylcyclotetrasiloxane and 2.42 mass% of (a2-1) tetramethyldivinyldisiloxane (molar ratio: D units in (a1-1)/(a2-1)=100) was continuously passed through the column so that the polymerization temperature was 80° C. and the residence time was 20 minutes. However, when a portion of the reaction mixture was extracted and the volatile content was measured, it was 98 mass%, indicating that the reaction had not progressed at all.

[Comparative Example 3]
A cylindrical column having an inner diameter of 22 mm and a length of 120 mm was filled with (a3-1) cation exchange resin Amberlyst 15JS-HG DRY manufactured by Organo Corporation to about 80% of the internal volume, and then a mixture of (a1-1) octamethylcyclotetrasiloxane 99.52 mass% and (a2-1) tetramethyldivinyldisiloxane 0.48 mass% (in molar ratio, D units in (a1-1)/(a2-1)=525, i.e., f+g+h+i=527 in the average composition formula (3)) was continuously passed through the column so that the polymerization temperature was 80° C. and the residence time was 50 minutes. However, the viscosity of the reactants increased, and the reaction could not be continued at the set flow rate. In addition, the internal pressure in the cylindrical column became too high, making it difficult to scale up the formulation from the standpoint of safety.

[Comparative Example 4]
A 300 ml separable flask equipped with a thermometer and stirring blade and purged with nitrogen was charged with 149.8 g (2.0 mol of D units) of octamethylcyclotetrasiloxane (a1-1), 3.7 g (0.02 mol) of tetramethyldivinyldisiloxane (a2-1), and 0.0046 g (30 ppm with respect to the total amount of (a1-1) and (a2-1)) of KOH as a catalyst, and heated with stirring for 20 minutes at 150° C. However, when a portion of the reaction mixture was extracted and the volatile content was measured, it was found to be 41% by mass, indicating that the reaction had not progressed sufficiently.

[Comparative Example 5]
A 300 ml separable flask equipped with a thermometer and stirring blade and purged with nitrogen was charged with 149.8 g (2.0 mol of D units) of octamethylcyclotetrasiloxane (a1-1), 3.7 g (0.02 mol) of tetramethyldivinyldisiloxane (a2-1), and 0.092 g (600 ppm with respect to the total amount of (a1-1) and (a2-1)) of trifluoromethanesulfonic acid as a catalyst, and the mixture was heated and stirred at 50° C. for 20 minutes. However, when a portion of the reaction mixture was extracted and the volatile content was measured, it was found to be 35% by mass, indicating that the reaction had not progressed sufficiently.

[Comparative Example 6]
A 300 ml separable flask equipped with a thermometer and stirring blade and substituted with nitrogen was charged with 149.8 g (2.0 moles of D units) of octamethylcyclotetrasiloxane (a1-1), 3.7 g (0.02 moles) of tetramethyldivinyldisiloxane (a2-1), and 0.0046 g (30 ppm relative to the total amount of (a1-1) and (a2-1)) of KOH as a catalyst, and the mixture was heated and stirred at 150° C. for 8 hours. A portion of the reaction mixture was withdrawn and the volatile content was measured, which was 13 mass %, confirming that the reaction had progressed. 0.060 g of 2-chloroethanol (molar ratio of 2-chloroethanol/KOH=9) was added thereto, and the mixture was heated and stirred at 150° C. for 1 hour (neutralization step). The resulting reaction product was subjected to vacuum stripping at 150° C. and 5 mmHg for 3 hours to obtain an alkenyl group-containing organopolysiloxane (A-8) represented by the following average compositional formula and having a viscosity of 180 mPa·s at 25° C. The weight average molecular weight was 11,200, and the proportion of vinyl groups was 0.028 mol/100 g (theoretical value: 0.026 mol/100 g).
(A-8)

[Comparative Example 7]
In a 300 ml separable flask equipped with a thermometer and stirring blade and substituted with nitrogen, 149.8 g (2.0 moles of D units) of octamethylcyclotetrasiloxane (a1-1), 3.7 g (0.02 moles) of tetramethyldivinyldisiloxane (a2-1), and 0.092 g (600 ppm relative to the total amount of (a1-1) and (a2-1)) of trifluoromethanesulfonic acid as a catalyst were added, and the mixture was heated and stirred at 50° C. for 4 hours. A portion of the reaction mixture was extracted and the volatile content was measured, which was 10 mass%, confirming that the reaction had progressed. 0.55 g (3,600 ppm relative to the total amount of (a1-1) and (a2-1)) of Kyoward 500SH manufactured by Kyowa Chemical Industry Co., Ltd. was added, and the mixture was heated and stirred at 50° C. for 2 hours (neutralization step). After removing Kyoward 500SH by filtration, the reaction mixture was placed in a separable flask and subjected to reduced pressure stripping at 150° C. and 5 mmHg for 3 hours to obtain an alkenyl group-containing organopolysiloxane (A-9) represented by the following average compositional formula and having a viscosity of 190 mPa·s at 25° C. The weight average molecular weight was 12,100, and the proportion of vinyl groups was 0.026 mol/100 g (theoretical value 0.026 mol/100 g).
(A-9)

As shown in the above Examples 1 to 7, the production method of the present invention makes it possible to obtain the desired alkenyl-containing organopolysiloxane in a very short time.
On the other hand, as shown in Comparative Example 1, when a linear organopolysiloxane with a high degree of polymerization was used as the terminal source, the reaction did not proceed due to the low reactivity of the linear organopolysiloxane.Also, as shown in Comparative Example 2, when a wet-type cation exchange resin was used as a catalyst, the reaction did not proceed, probably because the effect of the cation exchange resin as a catalyst was low.Furthermore, in Comparative Example 3, when the raw materials were mixed and charged in a specific ratio so that the set viscosity of the reactant was 1,500 mPa.s, the viscosity of the reactant became too high, making the production method unsuitable for continuous production.
In Comparative Examples 4 and 5, the reaction was carried out using KOH and trifluoromethanesulfonic acid, which have traditionally been used as catalysts, but because it takes time for these to reach equilibrium, the target product could not be obtained in a short reaction time. Therefore, in Comparative Examples 6 and 7, the reaction time of Comparative Examples 4 and 5 was extended, and the target products (A-8) and (A-9) were obtained. When the obtained (A-8) and (A-9) are compared with (A-1) obtained by the production method of Example 1, which differs only in the catalyst, there is no difference in physical properties, so that the production method of the present invention can obtain alkenyl group-containing organopolysiloxanes having performance equivalent to that of conventional products in an extremely short time compared to conventional production methods that use strong acids or strong bases as catalysts.

The manufacturing method of the present invention can produce low-viscosity alkenyl-containing organopolysiloxanes in a very short time. Furthermore, since the obtained alkenyl-containing organopolysiloxanes have low viscosity, they can be particularly suitably used in solventless curable organopolysiloxane compositions, and the cured films made of the compositions can be used as good release sheets.

Claims (4)

(a1) The following general formula (1):

(In the formula, ^R1 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and a is an integer satisfying 3≦a≦6.)
A cyclic organopolysiloxane represented by the formula:
(a2) The following average composition formula (2):

(In the formula, R ² 's are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, b is an integer of 2 or more, c is an integer of 0 or more, d is an integer of 0 or more, e is an integer of 0 or more, and 2≦b+c+d+e≦50, with the proviso that at least two of R ¹ and R ² are alkenyl groups.)
and _a ^linear or branched organopolysiloxane represented by _the following formula:
(a3) A method for producing an alkenyl group-containing organopolysiloxane represented by the following average composition formula (3), which comprises polymerizing in the presence of a cation exchange resin having a water content of 1.6 mass% or less for a reaction time of 20 minutes or less ( excluding those containing hexamethylcyclotrisiloxane as the (a1) cyclic organopolysiloxane) :

(In the formula, R3 ^'s are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, at least two of the ^R3 's are alkenyl groups, f is an integer of 2 or greater, g is an integer of 3 or greater, h is an integer of 0 or greater, i is an integer of 0 or greater, and 10≦f+g+h+i≦500.) The method for producing an alkenyl group-containing organopolysiloxane according to claim 1, in which the mixture of components (a1) and (a2) is continuously passed through a column packed with the cation exchange resin to carry out polymerization. 3. The method for producing an alkenyl-containing organopolysiloxane according to claim 1, wherein the cation exchange resin is a styrene-divinylbenzenesulfonic acid copolymer. 4. The method for producing an alkenyl-containing organopolysiloxane according to claim 1, wherein the alkenyl-containing organopolysiloxane represented by the average composition formula ( 3 ) has a viscosity at 25° C. of 1 to 1,000 mPa·s.